[jira] [Created] (DRILL-1362) Count(nullable-column) is incorrectly pushed into group scan operator

["Aman Sinha (JIRA)" <ji...@apache.org>]

Aman Sinha created DRILL-1362:
---------------------------------

             Summary: Count(nullable-column) is incorrectly pushed into group scan operator
                 Key: DRILL-1362
                 URL: https://issues.apache.org/jira/browse/DRILL-1362
             Project: Apache Drill
          Issue Type: Bug
          Components: Execution - Operators
    Affects Versions: 0.4.0
            Reporter: Aman Sinha


The following query on TPC-DS table web_returns produces wrong result because the aggregate count(wr_return_quantity) gets pushed into the parquet group scan operator even though wr_return_quantity is nullable and apparently the parquet metadata does not have stats on nullable column.  

0: jdbc:drill:zk=local> select count(wr_return_quantity) from web_returns;
+------------+
|   EXPR$0   |
+------------+
| 71763      |
+------------+

0: jdbc:drill:zk=local> explain plan for select count(wr_return_quantity) from web_returns;
{code:sql}
+------------+------------+
|    text    |    json    |
+------------+------------+
| 00-00    Screen
00-01      Project(EXPR$0=[$0])
00-02        Scan(groupscan=[org.apache.drill.exec.store.pojo.PojoRecordReader@e4acaad])
{code}

For reference, here are the correct results:  
tpcds=# select count(wr_return_quantity) from web_returns;
 count
-------
 68616
(1 row)

tpcds=# select count(*) from web_returns;
 count
-------
 71763
(1 row)



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